System of electrical distribution.



PATENTED JUNE 2, 1903.

`A. E. LUNE i SYSTEM 0E ELECTRICAL (DISTRIBUTION-l APPLICATION FILED DBO. 18,1899.

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UNTTnn STATES Patented June 2, 1 903.

PATENT OFFICE.

ALEXANDER D. LUNT, OF SCIIENECTADY, YORK, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, A CORPORATION OF NEXV YORK.

SYSTEM OF ELECTRICAL DISTRIBUTION.

:EEECJFECATION forming part of Letters Patent N o. 729,778, dated June 2, 1903.

Applieaticn filed December 18, 1899. Serial No. 740,631. (No model.)

to a point of neutral potential on the alternating-current-supply system.

The improvements comprised in the system to be described render possible the use of a small number of transformers in the alternatingcurrent-supply system, thus cheapening the cost of construction and somewhat reducing the complication of connections.

Other advantages flowing from my invention will be understood by reference to they following' detailed description, taken in connection with the accompanyingr drawings, while its scope will be particularly pointed out in the claims appended hereto. In the drawings,Figure 1 is a diagrammati representation of a system embodying` my invention, while Fig. 2 is an explanatory diagram. v

The drawings are intended to represent dia grammatically the conversion of three-phase alternating current into direct current, the operation taking place through the instrumentality of a rotary converter of a given number of phases upon which electromotive forces having a different phase relation are impressed. In the particular means shown the three-phase current is first supplied to a phase-changing transformer in the secondary windings of which quarter-phase electromotive forces are generated. The threephase mains are shown at 1 2 3, connected to which are leads 4E 5 (i of two interconnected transformers the primaries of which are shown at 7 8, The primary S has one terminal only connected to the three-phase mains, the other being connected to the middle point in the length oi' the primary winding 7, while, on the other hand, the winding 7 has both of its terminals connected to corresponding mains of the three-phase systenm The winding S has a number of turns somewhat less than that of the winding 7 and, more definitely speaking, in the proportion of V552. in the cores of the transformers will bear a quarter-phase relation to each other, as is well understood in the art. As a consequence the electromotive forces generated in the secondary windings of the transformers will have a like relation. As shown, the primary Sis provided with two secondary windings, (indicated at 9 10,) while the primary 7 ,on the other hand, is provided with but a single winding, (indicated at 11.) The six terminals of these three secondary windings are connected to the six collector-rings of a six-phase rotaryconverter, (indicated at C, and in order that the currents supplied to the converter may have the proper magnitudes to generate sixsphase magnetomo tive forces therein, as is required for its proper operation, these windings must be proportioned as to number'of turns in a manner represented theoretically by the electromotiveforce diagram designated as Fig. 2. The dotted circle represents the locus of the ends of the vector electromotive forces combined to produce resultant six phase currents. The line 12 connects points in the dotted circle displaced by one hundred and eighty degrees, while the lines 13 14, both of which are at right angles to the line 12, each connects points on the dotted circle separated by one-third of the circumference. lVith this arrangement of lines or of electroni otive forces which the lines represent the circle will be divided into six equal parts, each subdivision being connected to a line representing an electromotive force. If the dotted circle be supposed to represent an armature-winding of a rotary converter, while the lines shown be considered to represent sources of electromotive force of the phase relation and magnitude indicated, then by reason of the connections between the sources of electromotive forces afforded by the arma- As thus arranged the fluxes induced ture-winding resultant currents will iiow in ICO .motive force. In accordance with this plan of operation the secondary .1.1 of one of the supply-transformers heretofore referred to is made with a number of turns corresponding to the maximum alternating electromotive lforce which it is desired to impress upon the rotary converter. The terminals of this secondary are connected to collector-rings 15 1.6, which in turn are connected to dialnetrically opposite points of the armattire-winding 1V. This connection irresponds to the representation of the eleetromotive force l2 in' its inscribing circle in Fig. 2 referred to. Having chosen a certain magnitude for the electromotive force of the secondary l1, it is necessary that the secomlaries i) and 1.0 be suitably proportioned in order to properly cooperate therewith to produce resultant six-phase currents. To this end the electromotive force of each of these secoudarics should bear to that of the secondary 1l the same proportion as that existing between the electromotive forces 13 and l2 represented in Fig. 2. From the geometry oi' the/figure this proportion is as'x/ 3: 2. In showing the respective numbers of turns of the secondary windings it has not been possible in the drawings to represent this relation exactly, but someV approximation thereto has been made.

The terminals 'of the secondary 9 in aecordance with the diagram in Fig. 2 are connected to points of the converter-armature displaced by one-third ot' the polar pitch, the points of connection being such as to bring the point ol entrance of the current of the secondary 1l midway between them. This is shown at l() 17 in the drawings. In a similar manner the secondary 1 Ois connected to points .1S and lf), each of which is separated 'from the tap leadin to the opposite end of the secondary l1 by an angle corresponding to one-sixth of the polar pitch, the points 18 and l) being thus separated-from each other by one-third ol' the polar pitch. As thus arranged six-phase currents will circulate in the armature-windingof the converter C, by reason of which in the ordinary man- .ner direct currents are generated and, as indicated in Fig. l, are transmitted to directcurrent mains 20 and 2l. In the drawings the commutator, for clear-ness of illustration, is shown as disconnected from the armaturewinding; but it is to be understood that in practice the .ordinary connections will be made.

A neutral conductor O is shown as coopering with the direct-current mains 2O and 21 to form a three-wire system of direct-current distribution, this conductor being led back and connected to a point of neutral. potential. on the altei-nati11g-current s stem. This point is represented by the center of the inscribing circle, (shown in Fig'. 2,) and as this point lies upon the middle of the line 12, representing an eleetromotive l'orce, it will be seen that the point of neutral potential on the altern ating-current-supply system of Fig.

.winding, such as the windingdl() or 1l.

1. is found by tapping into the middle of the length of the secondary 11, since in carrying out the plan of operation indicated in Fig. the coil 11 was taken to represent the electromotive :force 12. The neutral conductor O is therefore brought back and connected to the point O in the secondary 11..

Although I have spoken of proportioniug the turns o't' the secondaries .l, 10, and 1X1. in accordance with the relations of the electromotive forces indicated in Fig. 2, it is to be understood that I have done so on the assumption that the volts per turn are equal. If the contrary is the case, the secondaries must be proportioned in such manner that the electromotive Aforces generated in the coils are in proper proportion to each other, as represented in Fig. 2, the :relation of electromotive forces being the real result to be obtained and not the relation of turns, which is, generally speaking, only an indication of the amount of electromotive force.

In the drawings the connections ot' the rotary converter are those corresponding to a bipolar vfield; but it will. be understood that these are to be correspondingly changed where a mulipolar structure is employed, as is usual in practice.

Vhen the sources of quarter-phase enrrents 9, 10, and 1l are connected to a translating device, such as a rotary converter, it will be evident that the circuits of the rotaryconverter armature serve to 'interlink the electromotive forces of the windings il, 10, and ll in the desired topographical relation to each other. Il the windings were not interlinked, it is evident that no difference o1'- potential would exist between a main leading' from one of the windingsas, 'for example, the winding` '.l-and a main leading from another Instead of depending upon the connections oli the windings to the rotary converter or other translating device as a means for interlinking the voltages of the supply' system I may make suitable permanent connections between the sources of current of different phase, the nature of which will be best understood by reference to Fig. 2, in which, for example, the .lines 13 and 12 represent, respeetively, intersecting electromotive forces of secondary windings of diiterent phase. This intersection forms a point of equipotential, and the secondaries whose electromotive forces are represented by these lines may consequently be connected together at corresponding points without normally causing l'low of current between the same. Thus the line 22 connects the middle point of the secondary S) with a point in the winding 11 located one-quarter of the distance from its end. This connection so far completes a circuit or circuits as to enable resultant current to flow when terminals of the secondaries are connected in circuit where without this connection no current would result. In a similar manner the middle point of the secondary ITO IIS

l0 is connected by a conductor with a point in the secondary il located one-quarter of the distance from its opposite end, this connection corresponding to the connection oi points on the lines of electromotive force l2 and lll represented by the intersection of these lines. liy reason of these equipotential'cimnectioit` 22 and 23 six-phase electromotive forces exist upon the terminals ot the secondary windings i), 10, and 11 regardless as to whether translating` devices are in circuit or not.

What l claim as new, and desire to secure by Letters Patent of. the United- States, is-

l. rlhc combination ot' three transformerwindings, means for generating electromotivc 'forces ot' the same phase in two of the windings, means for generatin in the other winding' an elcctromotivc force bearing a piartcrphase relation to the electromotive forces in the lirst two windings, and a six-phase alternating-current dynamo-electric machine supplied with current from said windings.

2. The combination of three transformerwindings, means for generating electroinotive t'orccs of the same phase in two ot' the windings, means for generating in the other winding an electromotive force having a quarterphase relation to the electroinotive forces in the iirst two windings, and conductors tying said windings together in such manner as to cause six-phase clectromotive forces to exist on mains leading` from said windings.

3. The combination ot' a dynamo-electric machine, a system of conductors upon which quarter-phase clectromotive forces are maintained, connections between a pair of conductors of one phase and points in a winding of said machine displaced by one-halt the polar pitch, and connections betii'een a pair ot' conductors of another phase and points in a winding' of said machine displaced by onethird of the polar pitch.

4f. The combination of a dynamo-electric machine, a system ol conductors upon which quarter-phase elcctromotive forces are maintained, connections between a pair of conductors of one phase and points in a winding of said machine displaced by one-half the polar pitch, and connections between a pair of conductors of another phase and points in a winding' of said machine displaced by onethird ot the polar pitch.

The combination of a dynamo-electric machine, a system of conductors upon which quarter-phase electromotive forces are maintained, connections between a pair of conductors ot one phase and points in a winding or said machine displaced by one-halt' the polar pitch, and connections between a pair of conductors of another phase and points in a winding of said machine displaced by less than halt the polar pitch.

I). The combination of a rotary converter having a number of phases represented by a multiple of three, transformer-wi]idings carryin g limiter-ph ase currents, and con dnctors connecting all of said windings to the armature of said converter, the points of connection of one of said windings being displaced from each other by an angle dilierent from the angle between the points of connection of another of said windings.

7. The combination of an alternating-current dynamo-electric machine of a nrunber of phases represented by a multiple et three, transformer-windin gs carrying quarter-phase currents, conductors connectingone ot said windings to said dynamo-electric machine at points displaced one-half ot the polar pitch, and conductors connecting another et' said windings to said dynamo-electric machine at points displaced one-third of the polar pitch.

S. The combination of a rotary converter, transformer-windings, two of which carry currents of the same phase while ra third carries current having a quarter-phase relation to the currents in the first two windings, and connections between the terminals of all oi" said windings and said converter.

l). The combination of a rotary converter, three transformer-windings, two oi which carry currents of the same phase while the third carries current having a quarter-phase relation to the currents inthe first two windings, and connections between all of said windings and said converter, the connections for the third winding being such as to embrace an are equal to one half the polar pitch. I

l0. The combination oil' a rotary converter, three transformer-windings, two ot' which carry currents of the same phase while the lthird carries current having a quarter-phase relation to the currents in the first two windings, connections between all of said windings and said converter, the connections for the third winding being such as to embrace an are equal to one-haltl the polar pitch, and a neutral conductor leading' from the middle point of the third winding.

ll. The combination of a rotary converter, transformer-windings carrying quarter-phase currents, conductors connecting one of said windings to the armature of said converter at points displaced by one-halt of the polar pitch, and conductors connecting other windings to points in the convertcr-armature displaced by less than half the polar pitch.

l2. The combination of a rotary converter, transformer-windings carrying' quarter-phase currents, conductors connecting one of said windings to the armature of said converter at points displaced by one-halt ot the polar pitch, a neutral conductor connected to an intermediate point in the last-mentioned winding, and conductors connecting other windings to points in the converter-armature displaced by less than half the polar pitch.

rlhe combination of a rotary converter, tran sf ormcr-windin gs carrying quarter-phase currents, conductors connecting one ot' said windings to the armature otsaid converter at points displaced by one-hall? of the polar IIO 1G. The combination of three windin generating quarter-phase clectromotive forces, two of said windings being` ol' the same phase and connections between the middle points respectively of the windings last mentioned, and separate points in the other winding, located substantiall)T one-hall" the distance between its middle point and its ends.

In witness whereof I have hereunto set my hand this 15th day of December, 1899.

ALEXANDER D. LUN'I.

itnesses z BENJAMIN B. HULL, MABEL E. JACoBsoN. 

